Switchable finger lever

ABSTRACT

The invention proposes a switchable finger lever ( 1 ) for a valve train of an internal combustion engine, said finger lever ( 1 ) comprising an inner lever ( 2 ) comprising on an underside ( 3 ) on one end ( 4 ), a support ( 5 ) for a gas exchange valve and on another end ( 6 ), a contact surface ( 7 ) for a head of a support element, said inner lever ( 2 ) being flanked by outer arms ( 8 ) which are articulated for pivoting relative to the inner lever ( 2 ) on a side of the one end ( 4 ), at least each of said outer arms ( 8 ) comprising on an upper side ( 9 ), a cam contacting surface ( 10 ), said inner lever ( 2 ) comprising directly next to the contact surface ( 7 ) a coupling device ( 11 ) for an optional connection of the outer arms ( 8 ) to the inner lever ( 2 ), said coupling device ( 11 ) comprising a cross-bore ( 12 ) in which two coupling slides ( 13 ) are arranged diametrically opposite each other, which coupling slides ( 13 ) for effecting coupling engage partially in or under an entraining surface ( 14 ) arranged on the respective outer arm ( 8 ) ending in this region, and the at least one restoring spring ( 15 ) being likewise arranged in the region of the another end ( 6 ) while being clamped between the inner lever ( 2 ) and the outer arms ( 8 ).

FIELD OF THE INVENTION

The invention concerns a switchable finger lever for a valve train of aninternal combustion engine, said finger lever comprising an inner levercomprising on an underside on one end, a support for a gas exchangevalve and on another end, a contact surface for a head of a supportelement, said inner lever being flanked by outer arms which areconnected to and pivotable relative to the inner lever, at least each ofsaid outer arms comprising on an upper side, a cam contacting surface,said inner lever comprising a coupling device for connecting the outerarms to the inner lever, and at least one restoring spring being clampedbetween the inner lever and the outer arms.

BACKGROUND OF THE INVENTION

A drawback of the known prior art switchable finger levers is that theyhave a too solid structure and a too complicated design, while offeringonly restricted variability and possessing an excessively high massmoment of inertia. Thus, for instance, the outer arms of the prior artswitchable levers are connected through crossbars, so that they have abox-like geometry which, in addition, is relatively complex from amanufacturing point of view. Moreover, important components such asrestoring springs for the outer arms and/or a coupling device arepositioned on the end situated at a distance from the fulcrum of thefinger lever, and this has an important influence in raising the massmoment of inertia. Finally, it is noted that, if a coupling slide isused to connect two outer arms for effecting coupling, the couplingdevices only offer an inadequate protection from switching errors.

OBJECT OF THE INVENTION

It is therefore an object of the invention to provide a switchablefinger lever of the pre-cited type in which the aforesaid drawbacks areeliminated.

SUMMARY OF THE INVENTION

The invention achieves the above object by the fact that the outer armsare articulated on a side of the one end on the inner lever, thecoupling device for an optional connection either of one of the outerarms or both outer arms simultaneously to the inner lever is situateddirectly next to the contact surface of the coupling device, thiscoupling device comprises a cross-bore in which two coupling slides arearranged diametrically opposite each other and which, for effectingcoupling engage partially in or under an entraining surface arranged onthe respective outer arm ending in this region, and the at least onerestoring spring is likewise arranged in the region of the another endwhile being clamped between the inner lever and the outer arms.

In this way, a switchable finger lever is provided in which theaforesaid drawbacks are eliminated. The finger lever comprises acoupling device with a simple structure arranged in the region of thecontact surface for the support element (transverse locking), in whichregion is likewise arranged the at least one restoring spring (lostmotion spring) for the outer arms.

A further contribution towards a light construction is obtained, ifaccording to one proposition of the invention, the outer arms are madeseparately. The crossbars of the prior art are dispensed with.

The separate outer arms enable, optionally, a three-step switching ofthe finger lever (zero lift/minimal lift-medium lift-full lift). Thus,in the case of a pressure chamber (pressure-less unlocking) beingarranged at a central position in the cross-bore, one of the couplingslides can be contacted by a strong compression spring and the othercoupling slide can be contacted by a compression spring weaker than saidstrong spring. During pressurizing of the pressure chamber withhydraulic medium in the cam base circle phase, that coupling slide is atfirst displaced to which the weaker compression spring is associated.The associated outer arm is then contacted, for instance, by a “mediumlift cam”, so that a “medium” valve lift is achieved. Upon furtherpressurization of the pressure chamber with hydraulic medium, thecoupling slide to which the stronger compression spring is associated isalso displaced, so that a full valve lift is obtained on the gasexchange valve.

On complete uncoupling of the outer arms, a minimal lift, for example,is generated on the inner lever through contact of a cam with acorrespondingly low cam lobe. However, it is likewise conceivable andintended to let the inner lever be contacted by a so-called zero liftcam, so that a deactivation of a valve is also possible. If appropriate,the contact of a cam on the inner lever can be dispensed with.

In the case of two equally strong compression springs being installed inthe cross-bore, the finger lever has the design of a so-called two-steplever. This enables a change-over between full lift/partial lift or fulllift/zero lift.

An upper side of the inner lever may comprise, for instance, a low-costsliding surface as a cam contact. However, it is likewise conceivableand intended to arrange a rolling bearing-mounted or a slidingbearing-mounted roller in a recess of the inner lever to serve as a camcontact.

The proposed transverse locking through two coupling slides on theanother end of the finger lever has a simple structure and, due to beingpositioned directly next to the contact surface, it contributes toreducing the mass moment of inertia. Similarly, a coupling region of thecoupling slides on the free ends of the outer arms has a simple design.Proposed is, for instance, a semi-shell-like cavity on each outer arm(cylindrical profile, gothic profile etc.) under which, for achievingcoupling, the coupling slide can be displaced with its smaller diameterstep. As engagement region for the respective coupling slide on theouter arm, it is, however, possible to use a bore or a flat. In case ofa flat, the contact region of the coupling slide can likewise have aflat configuration.

For mounting the outer arms on the one end, it is conceivable andproposed to use, among outer things, axle stubs projecting outwards fromthe inner lever. It is, however, also possible to arrange a continuousaxle in this region.

The invention includes two designs of the coupling device. According toa first variant, as set forth above, the coupling pistons are displacedinto their coupling position by hydraulic medium pressure, whereasuncoupling is realized through the force of compression springs. In thesecond variant, the coupling pistons are displaced in coupling directionby compression spring force and through hydraulic medium pressure inuncoupling direction. Conceivable and proposed is also to load them inboth directions by hydraulic medium or to displace them in at least onedirection through electromagnetic loading.

In the case of the two-step configuration of the switchable fingerlever, coupling through the two coupling slides which can be displacedoutwards on both sides offers a good protection from switching errors.Thus, a high cam lift is transmitted even if only one of the couplingslides is displaced outwards.

According to a further feature of the invention, a stop in the form of asnap ring or the like is arranged in an annular groove in the region ofa center of the cross-bore. In their retracted position, the couplingslides come to a standstill against this stop. At the same time, aminimal volume of the pressure chamber is guaranteed for the hydraulicmedium.

As already described above, the at least one restoring spring for theouter arms also extends in the region of the another end, so that afurther contribution to reducing the mass moment of inertia is made. Ina further development of the invention, it is proposed to use twotorsion leg springs, with exactly one torsion leg spring cooperatingwith one outer arm.

A simple mounting of the torsion leg springs is realized if these extendwith their coil assembles on axle stubs protruding laterally from theanother end of the inner lever. For reducing friction work, theinvention further proposes to configure the flanks of the second legs inmesh with the support of the respective outer arm so as to correspond atleast partially to an involute toothing of gearwheel teeth in mesh witheach other. It is clear that a sliding-free rolling contact cannot beachieved at every point of contact. However, the person skilled in theart should optimize the meshing region such that push-type sliding isminimized.

As a contact surface of the inner lever for the support element may beused, for instance, a semi-spherical cavity. Through this cavity,hydraulic medium can be routed via a branch channel into the pressurechamber of the cross-bore, which hydraulic medium, during operation ofthe finger lever, is made available out of a head of the supportelement.

BRIEF DESCRIPTION OF THE DRAWING

The invention is described more closely in the following with referenceto the appended drawing in which the figures show:

FIG. 1, a three-dimensional view of a finger lever of the invention,seen from the another end;

FIG. 2, a three-dimensional view of the finger lever of FIG. 1, in aviewing direction on its longitudinal sides, and

FIG. 3, a cross-section through the finger lever in the region of itscross-bore.

DETAILED DESCRIPTION OF THE DRAWING

The figures illustrate a switchable finger lever 1 for a valve train ofan internal combustion engine. The finger lever 1 comprises an elongateinner lever 2 flanked on each side by an outer arm 8. Both outer arms 8are articulated in the region of one end 4 on the inner lever 2.

On an underside 3, the inner lever 2 comprises in the region of the oneend 4 a support 5 for a gas exchange valve. In the region of another end6, the inner lever 2 comprises a contact surface 7 configured in thepresent case in the form of a semi-spherical cavity for mounting a headof a support element.

As can be seem in FIGS. 1 and 2, a cam contacting surface 10 configuredas a sliding surface is arranged on an upper side of 9 of each outer arm8. In the inner lever 2, in contrast, is arranged a cam contactingsurface 38 which is configured as a rotating roller and protrudesslightly beyond an upper side 20 of the inner lever 2.

In the region of the another end 6, the finger lever 1 comprises across-bore 12 arranged near the contact surface 7. Two coupling slides13 extend in the cross-bore 12 while being situated diametricallyopposite each other. Each coupling slide 13 has a two-step configurationand comprises an axially inner large diameter step 22 and an axiallyouter diameter step 23 that is smaller than the large diameter step 22.Both axially inner diameter steps 22 extend directly in the cross-bore12. In the coupled state, the respective outer diameter steps 23 engageunder an entraining surface 14 configured as a semi-shell-like cavity onthe underside 30 of each outer arm 8.

The coupling slide 13 shown on the left in FIG. 3 is guided by anannular step 24 extending integrally from the inner lever 2. Theright-hand coupling side 13, in contrast, extends through a separateannular step 25 configured in the form of a plug. Inner front ends 16 ofthe coupling slides 13 define a pressure chamber 18 for the couplingdevice 11. A supply of hydraulic medium to the pressure chamber 18 iseffected through a branch channel 21 starting from the contact surface7.

In opposite direction to the hydraulic medium pressure (uncouplingdirection), each coupling slide 13 is loaded through the force of acompression spring 19. Each compression spring 19 is supported axiallyinside on a front end 17 of the respective coupling slide 13 between thediameter steps 22, 23. Axially outside, the compression springs 19 actagainst respective inner sides of the annular steps 24, 25.

Directly on the another end 6 of the inner lever 2, two axle stubs 32protrude sideward. A restoring spring 15 configured as a torsion legspring is seated through its coil assembly 31 on each axle stub 32. Afirst, outer leg 33 of each restoring spring 15 acts against an upperside of a stop 35 protruding laterally from the inner lever 2. A second,inner leg 34 of each restoring spring 15 acts against a support 36 onthe underside 30 of the corresponding outer arm 8. Flanks of the secondlegs 34 in mesh with the support 36 correspond at least partially to aninvolute toothing of gearwheel teeth in mesh with each other.

FIGS. 1, 3 show the coupled state of the finger lever 1, in which thefinger lever 1 follows a lift of the high lift cams which act on the camcontacting surfaces 10 of its outer arms 8. For realizing this coupledposition, hydraulic medium is routed through the branch channel 21 intothe pressure chamber 18, so that, in the cam base circle phase, thecoupling slides 13 are displaced in opposition to the force of theircompression springs 19, under their entraining surfaces 14 on the outerarms 8.

When the hydraulic medium pressure is shut off, the coupling slides 13are displaced during the cam base circle phase through the force oftheir compression springs 19 out of contact with their entrainingsurfaces 14 in the outer arms 8, so that the outer arms 8 swing withoutload and the finger lever 1 follows only the lift of the low-lift camwhich contacts the inner lever 2.

If the compression springs 19 in the cross-bore 12 are designed withdifferent strengths from each other, the finger lever 1 can be switchedto three different valve lifts. For example, if the force of thecompression spring 19 illustrated on the left is weaker than the forceof the right-hand compression spring 19, upon pressurization of thepressure chamber 18 by hydraulic medium, the left-hand coupling slide 13is the first to move into the coupling position. As a result, the fingerlever 1 follows, for example, only a “medium-lift cam” which loads theleft outer arm 8. Upon further pressurization of the pressure chamber18, the coupling slide 13 with the stronger compression spring 19illustrated on the right in FIG. 3 is also displaced outwards into thecoupling position, so that the finger lever 1 then follows a high-liftcam which contacts the right outer arm 8 as shown in FIG. 3.

An uncoupling of the outer arms 8 is achieved through a stepwisereduction of the hydraulic medium pressure in the pressure chamber 18,needing no further specification here.

List of Reference Numerals

-   1 Finger lever-   2 Inner lever-   3 Underside-   4 One end-   5 Support of gas exchange valve-   6 Another end-   7 Contact surface-   8 Outer arm-   9 Upper side of outer arm-   10 Cam contacting surface of outer arm-   11 Coupling device-   12 Cross-bore-   13 Coupling slide-   14 Entraining surface-   15 Restoring spring-   16 Front end, inner front end-   17 Front end, outer front end-   18 Pressure chamber-   19 Compression spring, compression spring assembly-   20 Upper side-   21 Branch channel-   22 Large diameter step-   23 Small diameter step-   24 Annular step-   25 Annular step-   26 Annular stop-   27 Outer front end of annular step-   28 Outer front end of annular step-   29 Longitudinal side of inner lever-   30 Underside of outer arm-   31 Coil assembly-   32 Axle stub-   33 First leg-   34 Second leg-   35 Stop-   36 Support-   37 Contact region-   38 Cam contacting surface of inner lever-   39 Center stop

1. A switchable finger lever (1) for a valve train of an internalcombustion engine, said finger lever (1) comprising an inner lever (2)comprising on an underside (3) on one end (4), a support (5) for a gasexchange valve and on another end (6), a contact surface (7) for a headof a support element, said inner lever (2) being flanked by outer arms(8) which are articulated for pivoting relative to the inner lever (2)on a side of the one end (4), at least each of said outer arms (8)comprising on an upper side (9), a cam contacting surface (10), saidinner lever (2) comprising directly next to the contact surface (7) acoupling device (11) for an optional connection either of at least oneof the outer arms (8) or both outer arms (8) simultaneously to the innerlever (2), said coupling device (11) comprising a cross-bore (12) inwhich two coupling slides (13) are arranged diametrically opposite eachother, which coupling slides (13, for effecting coupling engagepartially in or under an entraining surface (14) arranged on therespective outer arm (8) ending in this region, and the at least onerestoring spring (15) being likewise arranged in a region of the anotherend (6) while being clamped between the inner lever (2) and the outerarms (8).
 2. Finger lever according to claim 1, wherein for displacementof the coupling slides (13) in one direction, a pressure chamber (18)for hydraulic medium is formed in front of one front end (16, 17) of thecoupling slides (13), which hydraulic medium can be routed via thecontact surface (7) out of the head of the support element, and fordisplacement of the coupling slides (13) in an opposite direction, atleast one compression spring/one compression spring assembly (19) actsagainst another front end (17, 16) of the coupling slides (13). 3.Finger lever according to claim 2, wherein, if one compressionspring/compression spring assembly (19) is used per coupling slide (13),the compression springs/compression spring assemblies (19) of thecoupling slides (13) are identically designed.
 4. Finger lever accordingto claim 3, wherein the cam contacting surfaces (10) of the outer arms(8) are configured for a contact by similar high lift cams, whereas anupper side (20) of the inner lever (2) does not serve for any camcontact or serves for a contact for a zero lift cam or a low lift cam.5. Finger lever according to claim 2, wherein, if one compressionspring/compression spring assembly (19) is used per coupling slide (13),the compression springs/compression spring assemblies (19) of the twocoupling slides (13)) are designed with different spring forces. 6.Finger lever according to claim 5, wherein, if the pressure chamber (18)is configured in front of inner front ends (16) of the coupling slides(13) for a hydraulic displacement of the coupling slides (13) incoupling direction [uncoupling direction through compression springforce], the cam contacting surface (10) of the outer arm (8) on a sideof a stronger one of the compression springs/compression springassemblies serves for a contact for a high lift cam, whereas the camcontacting surface (10) of the outer arm (8) on a side of a weaker oneof the compression springs/compression spring assemblies (19) serves asa contact for a medium lift cam, and an upper side (20) of the innerlever (2) does not serve for any cam contact or serves for a contact fora zero lift cam or a low lift cam.
 7. Finger lever according to claim 5,wherein, if the pressure chamber (18) is configured in front of outerfront ends (17) of the coupling slides (13) for a hydraulic displacementof the coupling slides (13) in uncoupling direction [coupling directionthrough compression spring force], the cam contacting surface (10) ofthe outer arm (8) on a side of a weaker one of the compressionsprings/compression spring assemblies (19) serves for a contact for ahigh lift cam, whereas the cam contacting surface (10) of the outer arm(8) on a side of a stronger one of the compression springs/compressionspring assemblies (19) serves as a contact for a medium lift cam, and anupper side (20) of the inner lever (2) does not serve for any camcontact or serves for a contact for a zero lift cam or a low lift cam.8. Finger lever according to claim 2, wherein the pressure chamber (18)is arranged centrally in the cross-bore (12) in front of inner frontends (16) of the coupling slides (13) and is intersected by a branchchannel (21) for the hydraulic medium out of the contact surface (7),wherein each coupling slide (13) comprises an axially inner diameterstep (22) which bears with an outer peripheral surface against thecross-bore (12) and an axially outer diameter step (23) of smallerdiameter than the axially inner diameter step (22), with which smallerdiameter step (23) the coupling slide (13) is guided through an axiallyouter annular step (24, 25) of the cross-bore (12), and between whichannular step (24, 25) and an annular stop (26) between the diametersteps (22, 23) of the coupling slide (13) the compressionspring/compression spring assemblies (19) is seated.
 9. Finger leveraccording to claim 8, wherein a center stop (39) such as a ring elementor a pin is arranged in the cross-bore (12) and serves to limit aninward displacement of the coupling slide (13).
 10. Finger leveraccording to claim 1, wherein the cross-bore (12) comprises an annularstep (24, 25) on both sides, outer front ends (27, 28) of said annularsteps (24, 25) are at least substantially flush with longitudinal sides(29) of the inner lever (2) and wherein one annular step (24) on oneside is an integral part of the inner lever (2) and the other annularstep (25) on the other side is a separate plug.
 11. Finger leveraccording to claim 1, wherein the entraining surfaces (14) of the outerarms (8) are configured as one of semi-shell-like cavities,quarter-shell-like cavities, bores or flats on undersides (30) of theouter arms (8).
 12. Finger lever according to claim 1, wherein the outerarms (8) are made as separate parts from each other.
 13. Finger leveraccording to claim 1, wherein two restoring springs (15) configured astorsion leg springs are arranged on the another end, a coil assembly(31) of each torsion leg spring is seated on an axle stub (32) whichprotrudes in a region of the another end (6) from a longitudinal side(29) of the inner lever (2), wherein a first leg (33) and a second leg(34) extends away from each coil assembly (31), which first leg (33) isclamped against a stop (35) of the inner lever (2) and which second leg(34) is clamped against a support (36) of the underside (30) of therespective outer arm (8).
 14. Finger lever according to claim 13,wherein flanks of the second legs (34) in mesh [contact region (37)]with the support (36) of the respective outer arm (8) correspond atleast partially to an involute toothing of gearwheel teeth in mesh witheach other.
 15. Finger lever according to claim 1, wherein the camcontacting surfaces (10) of the outer arms (8) are configured as slidingsurfaces and, if a cam contacting surface (38) is configured on an upperside (20) of the inner lever (2), this cam contacting surface (38) isconfigured as one of a sliding surface or a rolling bearing-mountedroller or a sliding bearing-mounted roller.